Journal ArticleDOI
Rayleigh similarity solutions and boundary layer flow for concentrated suspensions
Nhan Phan-Thien,Alan L. Graham +1 more
TLDR
In this paper, a series of transient problems in the flows of concentrated suspensions were investigated to test the effects of particle migration on the evolution of concentration and velocity profiles, and the authors reported a similarity solution to a Rayleigh problem, where the boundary of the infinite half space is given a velocity proportional to the square root of time.Abstract:
We have investigated a series of transient problems in the flows of concentrated suspensions to test the effects of particle migration on the evolution of concentration and velocity profiles. First, we report a similarity solution to a Rayleigh problem, where the boundary of the infinite half space is given a velocity proportional to the square root of time. Next, the classical Rayleigh problem, where the boundary is impulsively started initially at a constant velocity, is examined. The structure of the kinematics resembles that obtained in the first problem, but the concentration does not have a similarity form, and tends asymptotically to a uniform profile at large time. Finally, we solve the flow of a suspension past a semi-infinite plate, and discuss its connection to the Rayleigh problem. In all three cases, our calculations reveal Newtonian kinematics in the practical limit of a L ⪡ 1 , where a is the particle size, and L is a viscous diffusion length scale. In addition we see vastly different time and length scales in the evolution of the velocity and the concentration profiles. The velocity develops faster in time (by O( a L ) 2 ), and extends further in space (by O( L a ) ) than the concentration profile.read more
Citations
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Journal ArticleDOI
The shear-driven Rayleigh problem for generalised Newtonian fluids
TL;DR: In this article, the authors consider a variant of the classical Rayleigh problem, in which a semi-infinite region of initially quiescent fluid is mobilised by a shear stress applied suddenly to its boundary.
Journal ArticleDOI
Effects of demixing on suspension rheometry
TL;DR: In this paper, a modified version of the shear-induced migration model was introduced to predict transient torque reductions in torsional startup flows and transient pressure drop reductions in capillary developing flows.
References
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Book
Boundary layer theory
TL;DR: The flow laws of the actual flows at high Reynolds numbers differ considerably from those of the laminar flows treated in the preceding part, denoted as turbulence as discussed by the authors, and the actual flow is very different from that of the Poiseuille flow.
Journal ArticleDOI
The shear-induced migration of particles in concentrated suspensions
TL;DR: In this article, it was shown that shear-induced migration of particles out of the sheared Couette gap and into the fluid reservoir, which reduces the particle concentration in the gap and thereby the observed viscosity, is consistent with a gap-limited shearinduced diffusion process normal to the plane of shear, with the relevant diffusion coefficient being proportional to the applied shear rate.
Book
Similarity methods for differential equations
George W. Bluman,Julian D. Cole +1 more
TL;DR: In this paper, the authors define the notion of groups of transformations and prove that a one-parameter group essentially contains only one infinitesimal transformation and is determined by it.